New Anxiety

Hello. I am a 15 year old male, about to turn 16 in a few days. But, 3 weeks ago I had a panic attack after Tennis practice, and I forced my Mom to take me to the ER because we didn't know it was a panic attack because I've never had one. Sense then, I've had a panic attack at least twice a week. Except for one of those weeks, which was when I started taking Propanolol. Which is a blood pressure medicine, but in low doses can help anxiety and panic attacks, which it did. For one week I had no panic attacks, and I felt super great besides being out of breath from my low heartrate while on the medicine. But, after the first week while on the medicine, the effect wore off and I began to get side-effects, dizziness, short of breath, and I began to have panic attacks again, so we went to my doctor and he told me we couldn't up the doseage on the medicine because otherwise my already low heartrate, would drop to unsafe levels, so he took me immediately off of the medicine, which was safe because I was only on a 60 mg dose once a day, and we started Zoloft, which was 2 days ago, and sense then I've had one panic attack, but my mom has told me it takes a bit to actually start working so I'm praying it works. Any advice? These panic attacks have all felt super scary, with my chest getting tight, my body getting super hot and my limbs getting weak. I'm super scared for my health, even though my mom reminds me I'm a super healthy 15 year old male, so it must just be panic attacks, and no underlying condition.